1. Field of the Invention
The present invention relates to an optical component which selectively reflects a specific wavelength of propogating light and, in particular, to an optical fiber grating in which a core region of an optical fiber has a refractive index that changes periodically along its optical axis.
2. Related Background Art
Recently, as optical fiber communications technology advances, networks are becoming complex and signal wavelengths are being multiplexed thereby requiring a higher grade of system configuration. In such an optical communication system, the importance of optical circuit devices (optical components) has been increasing.
A fiber type element, as an example of typical configurations in optical components, is advantageous, for example, in that it has a small size and low insertion loss and can easily connect with an optical fiber. Known as such a fiber type element is a fiber type filter.
Recently, it has been well-known the refractive index of the core of silica type optical fibers that is doped with germanium oxide changes upon being irradiated with ultraviolet radiation. Studied and developed as a fiber type filter utilizing such a photoinduced refractive index change is an optical fiber type diffraction grating (optical fiber grating).
In this specification, the term "optical fiber grating" refers to an optical component comprising an optical fiber and a grating photowritten in the core region of the optical fiber.
The optical fiber type diffraction grating reflects a light component of light advancing through the optical fiber having a specific wavelength. In general, in order to make such a diffraction grating, a part of a core region of an optical fiber is irradiated with ultraviolet rays so as to form an area (grating) having a refractive index that changes periodically along the longitudinal direction (corresponding to a traveling direction of signal lights) of the core region.
In this specification, the center wavelength of light to be reflected by a grating is referred to as the reflection wavelength of the grating.